The present invention relates to a torque converter, which is used in an automobile transmission, and more particularly, to a lock-up mechanism-equipped torque converter having a lock-up mechanism, which can couple/uncouple an impeller and a turbine.
A torque converter is used in the automatic transmission of an automobile, and a lock-up clutch, which directly connects an impeller and a turbine, is often mounted to a torque converter. Engagement of the lock-up clutch heightens the mechanical efficiency of power transmission and improves gas mileage. Such a lock-up clutch mechanism is constituted by arranging a turbine-coupled lock-up piston (piston member) inside the space on the inner side of a converter cover (cover member), which covers a turbine, and links an engine output axis and impeller. In a lock-up clutch mechanism constituted in this manner, hydraulic pressure builds up inside a lock-up space enclosed by a lock-up piston and back face of a turbine in a space on the inner side of a converter cover, and the lock-up piston mates under pressure with the inner surface of the converter cover, an impeller and turbine are directly connected, and lock-up occurs.
However, it is known that the operating characteristics of such a lock-up mechanism change under the influence of torque converter internal pressure. For example, in a torque converter of a type in which a turbine blade is inserted into a slit formed in the turbine shell, bent up and fastened, because hydraulic fluid from inside the torque converter flows into the inside of the lock-up space through a crack in the slit, lock-up operating characteristics at deceleration are enhanced compared to a torque converter that does not have such a crack (for example, a torque converter of a type in which a turbine blade is soldered to the turbine shell). This is believed to occur because converter internal pressure rises at deceleration, causing hydraulic fluid to flow into the inside of the lock-up space via the above-mentioned crack, increasing the pressing force of the lock-up piston.
For this reason, a torque converter in which a communication-hole was formed in the turbine shell of a soldered-type torque converter was devised and put to practical use. However, the problem is that, when a communication-hole is formed in this manner, turbine internal pressure becomes lower than lock-up space internal pressure during slow acceleration, conversely causing lock-up operating characteristics to deteriorate.
Consequently, it has been proposed in Japanese Patent Laid-open No. H5-126231, and Japanese Patent Laid-open No. H8-105537, for example, that, in addition to forming a communication-hole that passes through the turbine shell into the lock-up space, there be provided a uni-directional valve (also called a check valve, or one-way valve) mechanism, which allows the flow of hydraulic fluid to the lock-up space side from the turbine side via this communication-hole, but prevents reverse flow. Further, in Japanese Patent Utility Model Publication No. H5-32687, it is proposed that, in addition to forming a communication-hole that passes through the turbine shell to the lock-up space, the part that forms this communication-hole be cut so that it is raised up on the inner side of the turbine, and is constituted so as to guide the flow generated inside the turbine at deceleration into the inside of the lock-up space.
However, a problem is that in order to configure a uni-directional valve mechanism, that many more extra parts are required in the turbine, thus raising costs, and another problem is that a torque converter turbine is operated at high speed, and under high pressure, and the operating characteristics, strength, durability, and reliability of a uni-directional valve mechanism are low. Further, in a constitution in which the part that forms a communication-hole is cut so that it is raised up on the inner side of the turbine, this raised part will function to a certain extent as a guide, which leads the flow of oil generated inside the turbine during deceleration into the inside of the lock-up space, but there is the danger that this function is weak, and instead, becomes the cause of flow disturbance, causing torque converter characteristics to deteriorate. Another problem is that there is the danger that the flow that occurs in the opposite direction from that at deceleration, like the flow of oil during slow acceleration, will also be disturbed, causing torque converter characteristics to deteriorate.
With the foregoing problems in view, it is an object of the present invention to provide a lock-up mechanism-equipped torque converter, which is a simple constitution that does not require extra parts, and which has a structure such that the operability of the lock-up mechanism can be improved as much as possible.
In the present invention, there is constituted a lock-up mechanism-equipped torque converter having an impeller member, which is coupled to an engine output shaft, a turbine member, which is coupled to a transmission input shaft, a stator member, which is maintained in a fixed state, a cover member, which covers the back side of the turbine member, and is connected to the impeller member (for example, converter cover 11a), and a lock-up mechanism, which causes the impeller member and turbine member to couple and uncouple. And the lock-up mechanism is constituted such that it is arranged inside a space enclosed by the cover member, and faces the inner surface of the cover member, and in addition, comprises a piston member (for example, lock-up piston 15), which is coupled to the turbine member, and lock-up is performed when hydraulic force builds up inside a lock-up space (for example, lock-up fastening chamber 17), which is enclosed by the piston member and back face of the turbine member in a space enclosed by the cover member, and the piston member is made to mate under pressure with the inner surface of the cover member.
In addition, there is formed in the turbine member a communication-hole, which opens facing a flow of hydraulic fluid generated inside the turbine in a predetermined direction, and, by connecting the inside of the turbine to the lock-up space, guides the predetermined direction flow into the inside of the lock-up space. Furthermore, this communication-hole is formed such that, for a hydraulic fluid flow that is the reverse of the predetermined direction flow, this reverse flow is disturbed only slightly by the communication-hole, and this reverse flow is restrained from moving inside the lock-up space via the communication-hole.
In a torque converter with a constitution such as this, because the communication-hole formed in the turbine member opens facing a flow of hydraulic fluid of a predetermined direction, hydraulic fluid inside the turbine is efficiently guided into the inside of the lock-up space from this opening, and the operating characteristics of the lock-up clutch improve in a state in which this predetermined direction flow is generated. Furthermore, because the communication-hole is formed such that a flow in the opposite direction thereto is not disturbed, and this reverse direction flow is restrained from moving into the inside of the lock-up space, there is no danger of lock-up clutch operating characteristics deteriorating by the inflow of hydraulic fluid into the inside of the lock-up space in a state in which this opposite direction flow is generated.
In a torque converter of the present invention, it is desirable that the above-mentioned communication-hole be formed such that it opens facing the flow of hydraulic fluid generated inside the turbine in the deceleration side direction at deceleration, and guides the deceleration side direction flow to the inside of the lock-up space, and, in addition, does not disturb a hydraulic fluid flow of opposite the deceleration side direction flow, and restrains this reverse direction flow from moving toward the inside of the lock-up space via the communication-hole.
In a torque converter of such a constitution, because the communication-hole (deceleration communication-hole) formed in the turbine member opens facing the flow of hydraulic fluid at deceleration, hydraulic fluid inside the turbine is efficiently guided into the inside of the lock-up space from this opening, and the operating characteristics of the lock-up clutch during deceleration improve. Engine braking action must be performed by engaging the lock-up clutch at deceleration, and since lock-up clutch operating characteristics improve like this, engine braking action is achieved quickly and efficiently. Furthermore, at acceleration, a flow opposite the deceleration side direction flow occurs inside the turbine, and because the communication-hole is constituted such that, for this flow, hydraulic fluid is restrained from moving toward the inside of the lock-up space via the above-mentioned opening, there is no danger of losing torque converter characteristics at acceleration.
It is desirable for the opening of the above-mentioned communication-hole (deceleration communication-hole) to be provided within a scope that extends from the radial inner diameter side bottom portion of the inner surface of the stator member, toward the outer diameter side, to the critical point of a turbine blade that constitutes the turbine member. Because turbine internal pressure increases at deceleration, and the flow of hydraulic fluid to the inside of the lock-up space from the turbine side is facilitated in this scope, deceleration lock-up all operating characteristics are further improved. Further, this is the scope wherein turbine internal pressure constitutes a relatively low pressure at acceleration, and providing a communication-hole within this scope does not impact the performance of the torque converter much at acceleration. That is, a communication-hole is provided in a scope that does not affect torque converter performance at acceleration. In accordance therewith, the communication-hole does not affect torque converter performance at acceleration, and this communication-hole enhances the operating characteristics of the lock-up clutch at deceleration.
In a torque converter of the present invention, the above-mentioned communication-hole (slow acceleration communication-hole) can be formed such that it opens facing the flow of hydraulic fluid generated inside the turbine in the slow acceleration side direction at slow acceleration, and guides the slow acceleration side direction flow to the inside of the lock-up space, and, in addition, restrains a hydraulic fluid flow of opposite the slow acceleration side direction flow from moving toward the inside of the lock-up space.
In a torque converter of such a constitution, because the communication-hole (slow acceleration communication-hole) formed in the turbine member opens facing the flow of hydraulic fluid at slow acceleration, hydraulic fluid inside the turbine is efficiently guided to the inside of the lock-up space from this opening, and the operating characteristics of the lock-up clutch during slow acceleration improve. Power transmission efficiency must be enhanced by engaging the lock-up clutch at slow acceleration, and since lock-up clutch operating characteristics improve in this manner, lock-up clutch engagement is performed quickly during slow acceleration. Furthermore, at deceleration, a flow opposite the slow acceleration side direction flow occurs inside the turbine, and because the communication-hole is constituted such that, for this flow, hydraulic fluid is restrained from moving toward the inside of the lock-up space via the above-mentioned opening, there is no danger of losing torque converter characteristics at deceleration.
It is desirable for the opening of the above-mentioned communication-hole (slow acceleration communication-hole) to be provided within a scope that extends from the radial outer diameter side end portion of the inner surface of the turbine member, toward the inner diameter side, to the critical point of a turbine blade that constitutes the turbine member. Because turbine internal pressure increases at slow acceleration, and the flow of hydraulic fluid to the inside of the lock-up space from the turbine side is facilitated in this scope, slow acceleration lock-up operating characteristics are further improved. Further, this is the scope wherein turbine internal pressure constitutes a relatively low pressure at deceleration, and providing a communication-hole within this scope does not impact the performance of the torque converter much at deceleration. That is, a communication-hole is provided in a scope that does not affect torque converter performance at deceleration. In accordance therewith, the communication-hole does not affect torque converter performance at deceleration, and this communication-hole enhances the operating characteristics of the lock-up clutch at slow acceleration.
Furthermore, for a torque converter of the present invention, it is desirable that it be constituted from a deceleration communication-hole, which is formed such that the above-mentioned communication-hole opens facing the flow of hydraulic fluid generated inside the turbine in the deceleration side direction at deceleration, and guides the deceleration side direction flow to the inside of the lock-up space, and, in addition, restrains a hydraulic fluid flow of opposite the deceleration side direction flow from moving toward the inside of the lock-up space, and from a slow acceleration communication-hole, which is formed such that it opens facing the flow of hydraulic fluid generated inside the turbine in the slow acceleration side direction at slow acceleration, and guides the slow acceleration side direction flow to the inside of the lock-up space, and, in addition, restrains a hydraulic fluid flow of opposite the slow acceleration side direction flow from moving toward the inside of the lock-up space.
If constituted in this manner, lock-up engagement characteristics can be improved during both deceleration and slow acceleration, and there is no danger of losing torque converter characteristics in either case.
Furthermore, in this case, it is desirable to provide the deceleration communication-hole and slow acceleration communication-hole by positioning them inside different passages in the plurality of passages inside a turbine that are partitioned and formed by turbine blades. In accordance therewith, when both communication-holes are provided inside the same passage, there is the danger that the respective communication-holes will synergistically disturb the flow inside the passage, but by providing them inside different passages, this kind of danger is eliminated, and torque converter performance can be maintained.
The constitution of the present invention is advantageous in that, because it is a simple constitution that provides in the turbine a communication-hole for which the opening direction is specified, manufacturing costs are low, and strength, durability and reliability are high. In addition thereto, it is also advantageous in that lock-up characteristics at deceleration, and lock-up characteristics at slow acceleration can both be enhanced. Further, in the present invention, this communication-hole can either be integrally press molded into the turbine shell itself, or a turbine having a communication-hole and blades can be integrally formed by casting.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.